Assertion (A) : Both `CO_2` snd ` SiO_2` have same structure .
Reason (R) : `CO_2` is a gas , whereas ` SiO_2` is a solid .

Options

A. If both (A) and (R) are correct and (R) is correct explanation of (A)
B. If both (A) and (R) are correct and (R) is not correct explanation of (A)
C. If (A) is correct , but (R) is incorrect
D. If (A) is incorrect but (R) is correct.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Analyze the Assertion
The assertion states that both CO₂ and SiO₂ have the same structure.

- **CO₂ (Carbon Dioxide)**: The structure of CO₂ is linear. It consists of one carbon atom double bonded to two oxygen atoms (O=C=O). This structure is simple and molecular in nature.

- **SiO₂ (Silicon Dioxide)**: The structure of SiO₂ is quite different. SiO₂ forms a three-dimensional network structure where each silicon atom is covalently bonded to four oxygen atoms in a tetrahedral arrangement. This results in a solid structure known as a covalent network solid.

**Conclusion for Step 1**: The assertion is **incorrect** because CO₂ and SiO₂ do not have the same structure.

### Step 2: Analyze the Reason
The reason states that CO₂ is a gas, whereas SiO₂ is a solid.

- **CO₂**: At standard temperature and pressure, CO₂ exists as a gas. This is due to the weak Van der Waals forces between CO₂ molecules, which allows them to move freely and exist in a gaseous state.

- **SiO₂**: SiO₂, on the other hand, is a solid at room temperature. This is due to the strong covalent bonds in its network structure, which hold the atoms in a rigid arrangement.

**Conclusion for Step 2**: The reason is **correct** because it accurately describes the physical states of CO₂ and SiO₂.

### Final Conclusion
- The assertion is incorrect: CO₂ and SiO₂ do not have the same structure.
- The reason is correct: CO₂ is a gas, while SiO₂ is a solid.

Thus, the correct answer is that the assertion is false and the reason is true.